A detector constructed from fabric is disclosed in international patent publication WO 00/72239. In this patent publication, the problem of false triggering is identified; usually resulting from a fabric detector having been folded to some extent. A solution is provided by the provision of five fabric layers in which two outer layers and a central layer are conductive and between each of these are provided insulating layers. It is therefore necessary for a mechanical interaction to exert pressure through two insulating layers and as a result of this false triggering does not occur and the fabric sensor may be folded without it producing an erroneous output signal.
The present applicant has identified a problem with the five layer system described above. The presence of the numerous layers and the requirement for two conducting layers to be acted upon in order to achieve conduction, means that the level of mechanical pressure required in order to achieve electrical conduction tends to vary between positions on the detector itself. The insulating layers usually take the form of nets and as such both of these layers will contribute to the variation in activation force, thereby increasing the overall variation over the device. Thus, if the detector is used to provide a keyboard for example, it may be necessary to apply different levels of pressure on different keys in order for the key to register as being pressed. Consequently in use, this tends to result in pressed keys not registering and accidental presses registering as key presses. The result often expresses itself as erroneous typing and clearly this is seen as a disadvantage when compared to the use of standard mechanical keyboards.